Hogan, William J.

e18524 Background: Venetoclax (Ven) in combination with hypomethylating agents (HMA) is FDA-approved front-line therapy for elderly or unfit patients with newly-diagnosed acute myeloid leukemia (ND-AML); however, majority relapse or are refractory ( Pratz AJH 2024 ). We examined survival outcomes in the setting of frontline Ven-HMA failure. Methods: ND-AML patients with failure to achieve complete remission (CR/CRi) or loss of CR/CRi after front-line Ven+HMA, excluding post-transplant relapse were retrospectively studied. Response was evaluated per European Leukemia Net 2022 criteria ( Dohner Blood 2022 ). Results: 356 patients with ND-AML (median age 75 years; 65% males; 55% secondary) receiving frontline Ven+HMA (median; 3 cycles (1-26), had refractory [n=219 (62%)], or relapsed disease [137 (38%)]. At diagnosis, karyotype was complex in 142/347 (41%). Mutations involved TP53 (29)%, ASXL1 (19%), RUNX1 (17%), SRSF2 (15%), KRAS/NRAS (13%), IDH2 (7%), FLT3-ITD (7%), NPM1 (6%) and IDH1 (5%). At treatment failure, complex karyotype was present in 72/180 (40%), including 55 from baseline. In 137 patients with paired NGS, mutations persisted in TP53 (88%), IDH1 (86%), IDH2 (78%), NPM1 (75%), K/NRAS (73%), RUNX1 (70%), FLT3-ITD (65%) mutations. Mutations were acquired in a minority [ IDH1 / IDH2 (2% each) TP53 (3%), NPM1 (4%), FLT3-ITD (5%) K/NRAS (6%)]. Clearance of mutations were infrequent for TP53 (12%) and IDH1 (14%). At median follow-up of 4 months (mo) (0-80) from the time of relapse/refractory disease, 320 (90%) patients have died, with median survival of 4 mo (1-2-3 yr survival 19%/8%/5%). On multivariate analysis, peripheral blasts >20%, complex karyotype, and wild-type IDH1 were independent predictors of inferior survival, while allogeneic stem cell transplant (ASCT) was associated with improved survival. A 3-point prediction model based on peripheral blasts ≥20%, complex karyotype, and wild-type IDH1 stratified patients into low-, intermediate-, and high-risk groups, with median survival of 7, 3, 2 months, respectively (p<0.01). 13 patients underwent ASCT (median survival; 22.5 mo; 3-yr survival 33%), from low (n=10) or intermediate-risk groups (n=3). Salvage therapy (n=170, 48%) yielded CR/CRi of 31% for Ven+HMA (n=36), 54% intensive chemotherapy (n=26), 50% FLT3 inhibitors (i) (n=22), 37% IDH1/2i (n=19), 25% other regimens (n=69). Median survival was similar: Ven+HMA 8 mo, intensive chemotherapy 10 mo, FLT3i 6.5 mo, IDH1/2i 14 mo, other regimens 6 mo, but inferior with supportive care (2 mo; p<0.01). Conclusions: The current study identifies peripheral blasts ≥20%, complex karyotype, and wild-type IDH1 as predictors of inferior survival in ND-AML relapsed/refractory to front-line Ven+HMA and underlines that while no specific salvage therapy conferred superior outcomes, ASCT was indispensable for long-term survival.